1. Technical Field of the Invention
The present invention relates to photostabilizing at least one dibenzoylmethane compound against UV radiation by at least one silicon-containing s-triazine substituted with two aminobenzoate or aminobenzamide groups.
This invention also relates to novel compounds and compositions, in particular cosmetic/dermatological compositions for topical application containing a combination of a dibenzoylmethane compound and a silicon-containing s-triazine substituted with two aminobenzoate or aminobenzamide groups.
2. Description of Background and/or Related and/or Prior Art
Light radiation with wavelengths in the range 280 nm to 400 nm is known to brown the human epidermis; more particularly, rays with a wavelength in the range 280 to 320 nm, known as UV-B, are known to cause erythema and cutaneous burns which may be deleterious to the development of a natural tan. For those and for aesthetic reasons, there is a constant demand for means for controlling natural tanning which can thereby control the color of the skin; thus UV-B radiation must therefore be screened.
It is also known that UV-A rays with wavelengths in the range 320 to 400 nm, which cause the skin to brown, tend to induce an impairment therein, in particular with sensitive skin or skin which is continually exposed to solar radiation. In particular, UV-A radiation causes the skin to lose elasticity and the appearance of wrinkles, resulting in premature aging of the skin. The radiation promotes triggering of the erythematous reaction or amplifies that reaction in certain subjects and may even be the cause of phototoxic or photoallergic reactions. Hence, for aesthetic and cosmetic reasons, such as preserving the natural elasticity of the skin, for example, more and more individuals seek to control the effect of UV-A radiation on their skin. Thus, screening UV-A radiation is also desirable.
With the goal of ensuring protection of the skin and keratinous material against UV radiation, sunscreen compositions are generally used which comprise organic screens which are active in the UV-A and active in the UV-B regions. The majority of such screens are liposoluble.
In this respect, a current particularly advantageous family of UV-A screens is constituted by dibenzoylmethane compounds, in particular 4-tert-butyl-4′-methoxydibenzoyl methane, which have intrinsically good absorbing powers. Such dibenzoylmethane compounds, which are now well known per se as screens which are active in the UV-A region, have been described in FR-A-2,326,405 and FR-A-2,440,933, as well as in EP-A-0,114,607; 4-tert-butyl-4′-methoxydibenzoyl methane is currently marketed under the trademark “Parsol 1789” by ROCHE VITAMINS.
Unfortunately, it has been discovered that dibenzoylmethane compounds are relatively sensitive to ultraviolet radiation (in particular UV-A), i.e., more precisely, they have an annoying tendency to degrade at a greater or lesser rate under the action thereof. This substantial lack of photochemical stability of dibenzoylmethane compounds to the ultraviolet radiation to which they are by their very nature intended to be subjected cannot guarantee constant protection during prolonged exposure to the sun, and repeated applications at regular, close intervals have to be made by the consumer to effectively protect the skin against UV radiation.
1,3,5-Triazine derivatives are particularly desirable in solar cosmetics because they are strongly active in the UV-B region. They have in particular been described in U.S. Pat. No. 4,367,390, EP-A-0,863,145, EP-A-0,517,104, EP-A-0,570,838, EP-A-0,507,691, EP-A-0,796,851, EP-A-0,775,698, EP-A-0,878,469 and EP-A-0,933,376; the following in particular are known:
2,4,6-tris[p-(2′-ethylhexyl-1′-oxycarbonyl)anilino]-1,3,5-triazine, or “Ethylhexyl Triazone” (INCI name), marketed under the trademark “Uvinul T 150” by BASF;
2-[(p-(tertiobutylamido)anilino]-4,6-bis-[(p-(2′-ethylhexyl-1′-oxycarbonyl)anilino]-1,3,5-triazine or “Diethylhexyl Butamido Triazone” (INCI name), marketed under the trademark “UVASORB HEB” by SIGMA 3V. They have a strong UV-B absorbing power and it would thus be highly advantageous to be able to use them in combination with the 4-tert-butyl-4′-methoxydibenzoylmethane noted above to obtain products offering broad effective protection over the entire UV radiation range.
However, it has been shown that certain of these 1,3,5-triazine derivatives, when in the presence of 4-tert-butyl-4′-methoxydibenzoylmethane, are photosensitive, namely to UV radiation, and suffer from the disadvantage of undergoing major chemical degradation. Under such conditions, a combination of these two screens could no longer provide the skin and hair with prolonged broad-based protection against the sun.